The present invention relates in general to fiber optic data communications, and more particularly, to a facility for automatically initializing a fiber optic communications link in one of a plurality of fiber control modes. The facility allows different types of open fiber control (OFC) channels to automatically communicate, as well as allowing an OFC capable channel to automatically communicate with a non-OFC channel.
Fiber optic communication links are an integral part of many computer systems. Certain of these data links employ a handshaking protocol known as xe2x80x9cOpen Fiber Controlxe2x80x9d (OFC). This protocol was originally developed and standardized by the ANSI X3T9 technical committee for laser safety purposes, since it allows the use of higher optical power levels (and corresponding longer distances) in a fiber optic link without violating international Class 1 laser safety standards if the link is broken or disconnected for any reason.
When a pair of transceivers with OFC are connected by a duplex fiber optic cable, the hardware performs a handshake to establish that both ends of the link are connected and observing the OFC protocol before lasers are turned on at full power for data transmission. The handshaking protocol begins with the lasers pulsed at a low power level for a long inactive period (typically 10 seconds) until the link is reconnected. At this point, each transceiver detects a pulse from the other end of the link with the proper duration and timing, which initiates the handshake; the lasers turn on to full power again only when the handshake completes successfully. If the link is opened for any reason (such as a broken fiber or pulled connector) then both ends of the link detect this event and automatically shut off their lasers fast enough to prevent any unsafe light exposure. Further details of OFC can be found in the ANSI Fiber Channel Physical and Signaling Interface (SC-PH), dpANS X3.230-199X.
Many types of systems employ OFC links for fiber channel data transmission. Although OFC links were the only method previously available to maintain laser safety while extending the distance of data links, their implementation has posed certain problems. These problems include requiring additional complexity in both hardware and system code to reset the OFC function as required, and both performance and service impacts in waiting the 10 second delay before the link becomes operational. Further, during maintenance and service the optical power and receiver sensitivity of an OFC link cannot be measured directly, since opening the link to attach a power meter would deactivate the lasers. Additional service tools such as an optical power splitter are thus required. The 10 second wait time is incurred each time the channel is taken off line or optical cables are changed, which may impact system availability and performance. Also, it is difficult to propagate OFC through an optical repeater, channel extender, or multiplexor without causing data link problems, which has made the implementation of these functions significantly more difficult when OFC is employed.
More recently, changes in laser safety standards have allowed higher optical powers, and thereby longer distance optical transmissions without requiring OFC. For the reasons stated above, it has therefore been desirable to remove OFC from future generations of coupling links in many systems. However, new systems must still inter-operate with a large number of OFC legacy systems in the field. The only alternative in use today is to support two different cards for each application, one for OFC and one for non-OFC links. This creates obvious problems of added cost and inventory tracking.
In view of the above, there exists a need in the art for an apparatus and method which can switch between OFC and non-OFC modes of operation as required by a particular application without compromising Class 1 laser safety.
Briefly summarized, the invention comprises in one aspect a method for automatically initializing a fiber optic data link in one of a plurality of fiber control modes. The method includes: automatically bringing up the fiber optic data link in one mode of a plurality of fiber control modes; determining whether the fiber optic data link initializes in the one mode; and automatically disabling the one mode if the fiber optic data link does not initialize and determining thereafter whether the fiber optic data link initializes in another mode of the plurality of fiber control modes.
In another aspect, a method for initializing a fiber optic data link in one of a plurality of modes is provided which includes: providing a plurality of fiber control modes within which the fiber optic data link can be initialized, wherein the plurality of fiber control modes includes at least one open fiber control (OFC) mode; selecting one mode of the plurality of fiber control modes in which to bring up and initialize the fiber optic data link; and providing hardware safety logic associated with the fiber optic data link to ensure disabling of the fiber optic data link if the data link is initialized in an OFC mode and the OFC mode is subsequently disabled.
System and program storage devices corresponding to the above-noted methods are also described and claimed herein.
To restate, provided herein is a technique for implementing a single system design which can function in either open fiber control (OFC) or non-OFC fiber optic links on demand. The technique includes providing auto-sense logic which senses whether a link is OFC or non-OFC and responds accordingly. Thus, no OFC software is required on new machine designs to keep the machines compatible with legacy OFC products. The auto-sense capability of the present invention is fully compliant with industry standard laser safety regulations for inherently safe Class 1 operation. Class 1 laser safety is ensured by turning off the transmitter when switching between OFC and non-OFC modes of operation.
Advantageously, the auto-sense capability of the present invention can be used to implement OFC using any type of standard optical transceiver with a laser disable function, including different voltage levels and small form factor optics which have no room for incorporating integrated OFC chips into their packaging. This also provides a cost savings compared with purchasing only 5-volt parts with integrated OFC logic in a larger package. Further, the present invention solves a problem with ambiguity in the OFC reset function present in many commercial OFC chips. Options include the ability to perform optical wrap with and without OFC, and to use signal detect from either the optics or the serialized/deserialized function. Further, the invention includes a redundant laser shutdown feature to ensure Class 1 laser safety under all operational mode changes from the host system. In particular, the invention includes a fail-safe mechanism to ensure that code bugs do not cause a laser safety problem.
Switching between OFC and non-OFC modes can be manually accomplished during configuration of a channel, or alternatively, logic can automatically sense whether the system is attached to an OFC or non-OFC channel and enable/disable OFC functions accordingly. This allows future products to inter-operate with legacy systems while taking advantage of performance improvements when the system is attached to non-OFC systems. It also removes the requirement to implement OFC control functions in the system code of new machines. The technique of the present invention can be readily incorporated into the design of optical repeaters and channel extenders. Also, as noted, secondary benefits include the ability to auto-sense different types of OFC signaling so that one channel could inter-operate with many different kinds of industry standard OFC-enabled equipment.
Additional features and advantages are realized through the techniques of the present invention. Other embodiments and aspects of the invention are described in detail herein and are considered part of the claimed invention.